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Differences in the immune response elicited by two immunization schedules with an inactivated SARS-CoV-2 vaccine in a
Nicolás M S Gálvez1,2, Gaspar A Pacheco1,2, Bárbara M Schultz1,2
1Millennium Institute on Immunology and Immunotherapy, Santiago, Chile.
Background:
The development of vaccines to control the coronavirus disease 2019 (COVID-19) pandemic progression is a worldwide priority. CoronaVac is an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine approved for emergency use with robust efficacy and immunogenicity data reported in trials in China, Brazil, Indonesia, Turkey, and Chile.
Methods:
This study is a randomized, multicenter, and controlled phase 3 trial in healthy Chilean adults aged ≥18 years. Volunteers received two doses of CoronaVac separated by 2 (0-14 schedule) or 4 weeks (0-28 schedule); 2302 volunteers were enrolled, 440 were part of the immunogenicity arm, and blood samples were obtained at different times. Samples from a single center are reported. Humoral immune responses were evaluated by measuring the neutralizing capacities of circulating antibodies. Cellular immune responses were assessed by ELISPOT and flow cytometry. Correlation matrixes were performed to evaluate correlations in the data measured.
Results:
Both schedules exhibited robust neutralizing capacities with the response induced by the 0-28 schedule being better. No differences were found in the concentration of antibodies against the virus and different variants of concern (VOCs) between schedules. Stimulation of peripheral blood mononuclear cells (PBMCs) with Mega pools of Peptides (MPs) induced the secretion of interferon (IFN)-γ and the expression of activation induced markers in CD4+ T cells for both schedules. Correlation matrixes showed strong correlations between neutralizing antibodies and IFN-γ secretion.
Conclusions:
Immunization with CoronaVac in Chilean adults promotes robust cellular and humoral immune responses. The 0-28 schedule induced a stronger humoral immune response than the 0-14 schedule.
Funding:
Ministry of Health, Government of Chile, Confederation of Production and Commerce & Millennium Institute on Immunology and Immunotherapy, Chile.
Clinical Trial Number:
NCT04651790.
Insights
The CoronaVac vaccine generates strong immune responses in adults. A 4-week interval between vaccine doses (0-28 schedule) resulted in a more robust antibody response compared to a 2-week interval (0-14 schedule).
Area of Science:
- * Immunology and Vaccinology
- * Infectious Disease Research
Background:
- * The COVID-19 pandemic necessitates global vaccine development.
- * CoronaVac, an inactivated SARS-CoV-2 vaccine, has demonstrated efficacy and immunogenicity in prior trials.
- * This study focuses on evaluating CoronaVac's immunogenicity in a Chilean adult population.
Purpose of the Study:
- * To assess the humoral and cellular immune responses to CoronaVac in healthy Chilean adults.
- * To compare the immunogenicity of two different dosing schedules: 2 weeks (0-14) versus 4 weeks (0-28) between doses.
- * To evaluate the correlation between neutralizing antibodies and cellular immune responses.
Main Methods:
- * A randomized, multicenter, controlled phase 3 trial involving 2302 healthy adults (≥18 years).
- * Participants received two doses of CoronaVac via either a 0-14 or 0-28 day schedule.
- * Humoral immunity was measured by antibody neutralization, and cellular immunity by ELISPOT and flow cytometry on peripheral blood mononuclear cells (PBMCs).
Main Results:
- * Both schedules induced significant neutralizing antibody capacities, with the 0-28 schedule showing a superior humoral response.
- * Antibody concentrations against SARS-CoV-2 and its variants of concern (VOCs) did not differ between schedules.
- * Cellular immune responses, including interferon-gamma secretion and CD4+ T cell activation, were observed in both groups, with strong correlations between neutralizing antibodies and T cell responses.
Conclusions:
- * CoronaVac immunization in Chilean adults elicits robust cellular and humoral immunity.
- * The 0-28 day dosing schedule is more effective in generating a stronger humoral immune response compared to the 0-14 day schedule.
- * The findings support the effectiveness of CoronaVac in inducing protective immune responses against SARS-CoV-2.
